In today's information age, communication devices typically support a number of different protocols that enable the communication devices to communicate over a data communication network. These various protocols are typically organized in layers, such that the protocol at a particular layer of the protocol stack provides communication services to the higher layer protocols and receives communication services from the lower layer protocols.
In order for the data communication network to be efficient, the data communication network is often divided into subnetworks. Communication devices within the same subnetwork communicate over a Local Area Network (LAN) using a LAN protocol, such as Ethernet or Token Ring, at a medium access control (MAC) protocol layer of the protocol stack. Communication devices on different subnetworks communicate using an internetwork protocol, such as the Internet Protocol (IP), IPX, or Appletalk, that requires routing at the internetwork protocol layer of the protocol stack. For convenience, a communication device that provides routing functions at the internetwork protocol layer of the protocol stack is commonly referred to as a “router.”
With the advent of Asynchronous Transfer Mode (ATM) networks, it was desirable to allow communication devices to be internetworked over the ATM network, and specifically over Virtual Channel Connections (VCCs) in the ATM network, in much the same was as those communication devices were internetworked over the LAN. Therefore, a LAN Emulation procedure was defined to allow such communication devices to be internetworked over the ATM network, and particularly over an emulated LAN (ELAN). The ELAN enabled those communication devices within the same subnetwork to communicate as if those communication devices were internetworked over the LAN.
Even though the ELAN enabled communication devices within the same subnetwork to communicate as if those communication devices were internetworked over the LAN, communication between communication devices on different subnetworks still required routing at the internetwork protocol layer of the protocol stack. Therefore, certain protocols were defined to allow communication devices on different subnetworks to communicate without requiring routing at the internetwork protocol layer of the protocol stack (or at least without requiring routing along the entire data path). One such protocol, known as Multi-Protocol Over ATM (MPOA), is described in ATM Forum Technical Committee documents entitled Multi-Protocol Over ATM Version 1.0 and Multi-Protocol Over ATM Version 1.1, which are hereby incorporated by reference in their entireties, and are referred to collectively hereinafter as the “MPOA specification”. MPOA allows communication devices to communicate in an ELAN environment without requiring routing through the ELAN at the internetwork protocol layer of the protocol stack. Specifically, MPOA allows those communication devices at the edge of the ELAN to establish a shortcut VCC through the ATM network and forward the inter-subnetwork data traffic over the shortcut VCC rather than route the inter-subnetwork data traffic at the internetwork protocol layer of the protocol stack. One technique for establishing such a shortcut VCC, which uses MPOA in conjunction with the Next Hop Resolution Protocol (NHRP), is described in the related patent application entitled ESTABLISHING SHORTCUTS IN A MULTIPROTOCOL-OVER-ATM SYSTEM, which was incorporated by reference above.
For various reasons, it is sometimes necessary or desirable for a communication network to be shared by multiple consumers. Because each of the consumers typically needs to maintain a certain amount of autonomy, the communication network is divided into a number of Virtual Private Networks (VPNs), where each VPN emulates a single, private network.
The present invention relates to the support of Virtual Private Networks (VPNs) in an MPOA/NHRP network.